Mass. Gen. Laws ch. 54 § 30A
Notwithstanding any contrary provision of section thirteen, where voting machines are used the city or town clerk or election commissioners shall appoint in writing one or more custodians of voting machines, who shall assist him or them in the preparation and upkeep of voting machines, shall instruct the election officers in the use of said machines, and shall perform their duties under the supervision of the city or town clerk or election commissioners. If a voting machine requires adjustment during the course of an election, a custodian shall, if requested to do so by the warden, make such repairs or adjustments as may be required to return the voting machine to operating condition, and for this purpose may enter within the guard rail in any polling place, but he shall not make any such adjustments or repairs except in the presence of not less than two election officers of the precinct, who shall be designated by the warden so as to give equal representation to the two leading political parties. No person holding an appointment as an election officer under section eleven shall be appointed a custodian under this section. No person shall be appointed or act as a custodian in a voting precinct where he is a candidate for election, nor shall such person be permitted to perform any work in advance upon a voting machine to be used in such a precinct.
Mass. Gen. Laws ch. 54, § 30A